Co-registration of optical coherence tomography (OCT) pullback image data and an angiographic X-ray image involves different problems than are involved in other types of pullback imaging registration such as IVUS (intra-vascular ultra sound) and angiography image registration. Since an IVUS pullback is performed without the injection of contrast agent into vessels, it is possible to image an IVUS catheter with X-ray during catheter pullback. OCT, however, requires contrast medium for its imaging, making the vessels radio-opaque and effectively hiding the catheter. An IVUS pullback is also performed slowly over a period of 1 to 3 minutes, allowing the catheter to be imaged multiple times such that each image of the catheter can be made at the same time within a heart cycle, thus substantially eliminating the effect of cardiac motion that distorts the shape of a catheter in a vessel being imaged. An OCT pullback is performed quickly, usually in less than 3 seconds. Even if it is possible to image an OCT catheter during the pullback, ECG-gated imaging of the catheter would only produce 2 or 3 frames. A system according to invention principles addresses these deficiencies and associated problems.